Thermoplastic composite pipes (TCPs) are becoming the ideal substitute for traditional steel pipe due to its superiorities including light weight and corrosive resistance. The cross-section of TCPs consists of an inner liner, a laminate layer, and an outer jacket. The laminate layer is made of multi-plies of helically wound continuous fibre reinforced unidirectional tape. In the present study, a three-dimensional (3D) theoretical model and a 3D finite element model were developed to analyse the stress state of a TCP under internal pressure. With a selected failure criterion for composite laminate, the ultimate burst pressure of a TCP can be predicted. By comparing the predicted burst pressure with the experimental results, several commonly used failure criteria were compared in terms of their accuracy.
Thermoplastic composite pipes (TCPs) are increasingly used to transport hydrocarbons and water in the oil and gas industry due to their superior properties including corrosion resistance, thermal insulation, light weight, etc. The cross-section of TCPs generally consists of three layers: inner liner, composite laminate, and outer jacket. Three layers are bonded together and form a solid-wall construction. Inner liner and outer jacket made of thermoplastic polymer provide protective barriers for the laminate to against the inner fluid and outer environment. The laminate is constructed by an even number of helically wounded continuous fiber reinforced thermoplastic composite tapes. In this study, mechanical behaviors of a TCP under an internal pressure were investigated by using analytical and finite element analysis (FEA) methods. The analytical method which is based on the three-dimensional (3D) anisotropy elastic theory can take account of non-uniformly distributed stress and strain through the thickness of the pipe wall. FEA models were setup by using the software ABAQUS to predict the stress distribution of the pipe. 3D Tsai-Wu failure criterion was used to predict the maximum internal pressure of the pipe. Effects of some critical parameters, such as the winding angle of composite tapes and the number of reinforced plies, on the internal pressure capacity of TCPs were studied. Results obtained from the analytical and FEA methods were fairly agreed with each other, which showed that with the increasing of the number of reinforced plies the internal pressure capacity of a TCP gradually increases and approaches to an extreme value. In addition, the optimal winding angle which results the maximum internal pressure is not a constant value, instead, it varies with the increasing thickness of the laminate layer. This study provides useful tools and guidance for the design and analysis of TCPs, and is currently under validation through experiments.
The cross section of thermoplastic composite pipes (TCPs) generally consists of three layers: inner liner, reinforcement laminate, and outer jacket, which are fully-bonded together to form a solid-walled structure. In this study, mechanical behaviors of a TCP under an internal pressure were investigated by using analytical and finite element analysis (FEA) methods. The analytical method which is based on the three-dimensional (3D) anisotropy elastic theory can take account of non-uniformly distributed stress and strain through the thickness of the pipe wall. FEA models were setup by using the software ABAQUS to predict the stress distribution of a TCP. 3D Tsai-Wu failure criterion was used to predict its maximum burst pressure. Effects of winding angles and number of reinforcement plies on the burst pressure of TCPs were studied. Results obtained from the analytical and FEA methods matched with each other, which showed that with the increasing of number of reinforcement plies the burst pressure of a TCP gradually increased to an asymptotic value. In addition, the optimal winding angle associated with the maximum burst pressure was not a constant value, instead, it varied with the increasing thickness of the laminate layer. This study provided useful tools and guidance for the design and analysis of TCPs, while further validation experiments are still needed.
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